Liquid crystal display (LCD) devices are devices that control the transmission or blockage of light (turning ON/OFF the display) by controlling the orientation of liquid crystal molecules having birefringence. Examples of liquid crystal orientation modes of LCDs include the twisted nematic (TA) mode in which liquid crystal molecules having positive dielectric anisotropy are oriented so as to be twisted at 90° when viewed from a direction normal to the substrate, vertical alignment (VA) mode in which liquid crystal molecules having negative dielectric anisotropy are oriented vertically with respect to the substrate surface, and in-plane switching (IPS) mode and fringe field switching (FFS) mode in which a horizontal electric field is applied to liquid crystal layer to orient liquid crystal molecules having positive dielectric anisotropy horizontally with respect to the substrate surface.
In VA mode, display is performed by using liquid crystal having negative dielectric anisotropy and applying a vertical electric field to the liquid crystal molecules, which are oriented vertically with respect to the substrate surface, such that the liquid crystal molecules take on a more horizontal orientation, but when the liquid crystal molecules are viewed at different angles, the apparent birefringence thereof differs, which results in narrow viewing angle.
A method in which the orientation of the liquid crystal is partitioned by a technique of applying pretilt angles using a polymer (polymer sustained alignment (PSA)). A method of partitioning the orientation of the liquid crystal is proposed in which a voltage is applied to a liquid crystal layer containing a photocurable monomer, the liquid crystal molecules are oriented in multiple azimuth directions along slits formed in the pixel electrodes, and ultraviolet light is radiated when the orientation azimuths are stable to cure the photocurable monomers, thereby fixing the azimuth directions of the liquid crystal molecules (see Patent Document 1, for example).
In IPS mode, display is performed by relying on the movement of liquid crystal molecules towards a horizontal orientation in response to a horizontal electric field formed between a pair of comb-shaped electrodes. In FFS mode, display is performed by relying on the movement of liquid crystal molecules towards the horizontal orientation in response to a horizontal electric field (fringe field) formed between a common electrode and a pixel electrode provided over the common electrode across an insulating layer. Although the viewing angle is improved in IPS mode and FFS mode, it is difficult to attain a contrast ratio comparable to that attained in VA mode.
Also, in recent years, a new method has been proposed in which the driving of liquid crystal is controlled by generating a vertical electric field in addition to the conventional horizontal electric field in a liquid crystal display device that performs display using a horizontal electric field as done in IPS mode and FFS mode (see Patent Documents 2 and 3, for example).